FROM STATION UPHEAVAL, A TRACKING NIGHTMARE

What a difference a year makes. And what a nightmare it's been for Nielsen Media Research and the agency media planners and buyers who depend on Nielsen ratings estimates to place local and national TV ad dollars.

In the year since New World Communications Co. Chairman Ronald Perelman and Fox leader Rupert Murdoch began the game of musical affiliate chairs, 22 markets have experienced at least one change in a major network affiliation. In some markets, such as Phoenix, at least three of the four network affiliates have changed hands.

The changes have put added pressure on Nielsen to monitor shifts and scrutinize ratings data, particularly in the nearly 200 non-metered markets that rely on viewers to fill out diaries about their TV viewing preferences.

One of the biggest challenges for media planners is that the shifts don't all occur at once and require constant scrutiny. In at least one market, stations dropped their network affiliation and then broadcast as independents before switching to their new affiliation. In other markets, stations rolled in programs from their new networks gradually.

"This has been an unprecedented shift in affiliation assignments and it's impacted the business in a very large way," said Ron Meyer, senior VP-group director of marketing for Nielsen Station Index. "It's impacted TV programming. It's impacted the TV ratings business. And it's impacted the way the consumer watches television."

Mr. Meyer said Nielsen has instituted safeguards and fail-safe procedures to monitor discrepancies between what diary-keepers report and what may actually be the case in markets.

Among other steps, he said, Nielsen will call every household that provides discrepant information.

The problem, said Nielsen VP Bob Paine, is that viewers may not always know what network they're watching, because concurrent with the affiliation shuffle, stations are joining with more than one network via secondary affiliations.

"There clearly are more stations today with secondary, and even tertiary affiliation, than there were a year ago," he said. "For example, there are some stations that may carry only part of one network's programming, like the Warner Bros. kids lineup, or the Fox football coverage."

Despite safeguards, some shifts in TV viewing patterns are bound to occur. The problem for media buyers is how to plan for the changes when investing advertising dollars.

"Right now, we're kind of at the mid-range point of these changes and we're starting to see some patterns emerging," said Kim Sullivan, local media supervisor at Cincinnati-based Media That Works, an independent media-buying company that has been tracking the changes closely.

"We were hoping that when we finished [an analysis of the first two switch markets, Cleveland and Kansas City] we'd have a pretty cut and dried look at the changes. But what we've found is a lot of roller-coaster affects in different dayparts," she said.

For former Big 3 stations shifting to Fox affiliates, Ms. Sullivan said, early morning and prime-time program ratings are down significantly; syndicated programming on all stations produced inconsistent patterns; and ratings for stations without affiliation changes were essentially unaffected.

"That last part was especially comforting for us, because it was an area that we went to to avoid the mess. Luckily, that has turned out to be a lifesaver," she said. But the media-buying company advised clients to avoid buying local news programming on stations undergoing switches, because it's the programming most closely linked to a station's local identity.